All About Spines

Dave Tutelman -- January 30, 2008

Back in February 2006, John Kaufman (the head guy at Club Scout, the frequency meter company) asked on the SpineTalker's forum,

Hi Folks,
Since things are so slow I have a simple question to ask. What are you trying to accomplish by spine aligning a shaft? Or maybe I should say trying to prevent? From all the talk I've heard over the years maybe this question isn't as trivial as it sounds.

Shaft spines are interesting because there is evidence that "aligning the spine" can affect the feel and/or performance of the golf club. Aligning the spine means rotating the shaft in the hosel, while building the club, so that the spine of the shaft points in some specific direction. For instance, the spine can be placed in the heel-toe plane of the club. Obviously, this has to be done at the time the shaft is installed in the clubhead.

The next day after John posted his query, there were a few responses along the lines of "we are trying to optimise the performance of a golf shaft within the rules of golf". That caused John to elaborate a bit:

I guess my simple question was too brief. You have stated all the results we hope to acheive by aligning shafts. But what causes these things to happen when you align a shaft?

John is right that the question is very non-trivial. I posted my initial thoughts in the form of an outline within about a month, but it took almost two years before I was ready to write it up as an article. Here it is.

Be forewarned, this is not the usual clubfitter's view of spines. It is spines as viewed by an engineer, so intuition and hand-waving are going to take a back seat. And, unfortunately, too much of what is "generally known" about spines falls under the heading of intuition and hand-waving. I'll try to point out where my views deviate from the "common wisdom", but I may not have done it everywhere.

Because of all the fallacies and misinformation about spines, among both the public and custom clubmakers, I'm going to start at the beginning and work my way from there to John's question.

Executive Summary

First, if all you want is advice on how to measure and align spines, here is a summary of the results. If you want to know why these are the results, you will have to read further than this summary.
  1. Don't use bearing-based spine finders to locate the spine; they give wrong answers. Use FLO (Flat Line Oscillation) instead.
  2. The high-frequency FLO plane is the pair of spines (separated by 180*); the low-frequency FLO plane is the pair of NBPs (again, separated by 180*). The spine plane and the NBP plane are separated by 90*.
  3. Corollary: if your instrument tells you that the spine is 180* from the NBP (instead of the proper 90*), throw away the procedure or the instrument that tells you that. It is giving you wrong answers.
  4. Measure the frequency difference between the FLO planes. If it's less than 3cpm, spine alignment is not going to do anything for performance or feel (though it may give you some peace of mind).
  5. There is no provable best direction for aligning the spine. Theories differ, and the experimental evidence is not conclusive. But most experiments and practice say to place the spine in the heel-toe plane and the NBP in the target plane. The most likely theories also support this alignment.
  6. If you want to ask whether to place the NBP toward the target or away from it, you weren't paying attention. Go back and read the points a-e again. The question makes no sense if you accept those points.
Now for a list of the points in the article, a sort of table of contents. Each consists of a link to the place in the article where the point is elaborated.

Basic definitions and physics

Finding and measuring spine

Both analysis and experimental evidence are presented to support this position.

Spine alignment

Finally we get to John's question: what are we doing to or for performance when we align the shaft in the club?

Loose ends

Some things that don't fit neatly into the other categories:

Bottom line...

We don't know nearly as much about spine alignment as most clubmakers would have you believe. And much of what we "know" may not be true. In fact, some of it is demonstrably false. 
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Last modified -- 10/12/2008